# How to calculate the ship resistance caused by water viscosity

If there is a ship going in the sea at 50km/h, and a length of 5m, width of 2m, how do I calculate the ship resistance caused by water viscosity? in other words I want to calculate the drag Force that should be made to overcome the water viscosity. I found this formula

$F=\frac{1}{2} ρv^2A c_d$

but I can't calculate "$c_d$" (drag coefficient)

• I tried to guess what you meant by the notation, you can correct it in any case. Also, it is always a good idea to specify what your symbols mean when stating an equation. – Void Sep 21 '14 at 10:01
• @JustMe - you need to specify the frontal cross-sectional area $A$ below the water line. For selection of the drag coefficient $C_d$ see: engineeringtoolbox.com/drag-coefficient-d_627.html – Johannes Sep 21 '14 at 10:28
• Also note that the water viscosity doesn't enter the equation. So you can't claim the ship resistance is caused by the viscosity of the water. – Johannes Sep 21 '14 at 10:30
• A Google search for hull drag would be a good place to start doing some research for yourself. Ignore the links related to drag queens in Hull - they are unrelated to ships. – John Rennie Sep 21 '14 at 11:06